The invention relates to a driving assistance device, in particular a device of this kind which is optimised by synergy with an adaptive lighting system, for a motor vehicle, allowing a following vehicle to keep its distance from a followed vehicle or target vehicle, freeing the driver from any need to take action at the accelerator pedal or brake pedal.
A device of this kind, generally designated by the abbreviation ACC (Automatic Cruise Control), is able to automatically influence the acceleration and braking of the following vehicle so as to adapt its speed to that of the target vehicle.
The driving assistance device comprises at least one emitter of radiation towards the front of the vehicle, at least one receiver for part of this radiation reflected by the target vehicle, and means of calculation and control for influencing the acceleration and braking of the following vehicle in accordance with the information coming from the emitter-receiver unit and in accordance with various other data pertaining to the following vehicle (speed, etc . . . ).
At the moment when the driving assistance device is activated, the driver of the following vehicle is invited to specify a reference speed (to which the vehicle will automatically return if the ACC mode is no longer required) and a reference xe2x80x9cflight timexe2x80x9d. This xe2x80x9cflight timexe2x80x9d corresponds to the time required, at a given moment, for the following vehicle to reach the position of the target vehicle in front of it. This flight time is commonly between 1 second and 2 seconds. Setting this flight time determines the distance which must be maintained between the following vehicle and the target vehicle at a given speed.
The emitter-receiver unit of the vehicle is generally of the radar or lidar type. The lidar comprises an infrared emitter with an optical sensor as a receiver.
When the ACC assistance device is activated, it searches to ascertain whether there is a vehicle capable of being followed along the axis of the following vehicle at a distance within a certain range according to a given detection angle and with a reasonable speed difference. When these conditions are satisfied, the driving assistance device indicates on the dashboard of the following vehicle that there is a potential target vehicle, and the driver can then decide to xe2x80x9cattach himselfxe2x80x9d to this vehicle by acting on a specific lever. From this moment, when the target vehicle accelerates or decelerates, the following vehicle automatically does the same. There are multiple safeguards.
It is possible that the following vehicle will lose track of the target vehicle, this generally corresponding to a normal operating mode: for example, the target vehicle has changed lane or has left the road at a junction, or the following vehicle itself has changed lane. In this case, the assistance device makes the following vehicle return progressively to its reference speed.
However, it can also happen that the following vehicle loses track of the target vehicle on a more or less pronounced bend or owing to confusion with other vehicles to the side when the target vehicle is still in front on the path of the following vehicle. The following vehicle then returns to its reference speed, which is generally higher than the instantaneous speed since there is a tendency to slow down on a bend. The following vehicle then rapidly catches up with the previous target vehicle without xe2x80x9cseeing itxe2x80x9d, giving rise to a risk to the driver.
Various solutions have been proposed: for example several beams or oscillatory beams for dynamic scanning of the emitter, but these methods are generally expensive if they are to be effective, or are not very effective when they are inexpensive.
It is the object of the invention, above all, to provide a driving assistance device of the type defined previously which no longer has the disadvantages mentioned above or has them to a lesser degree, and the cost price of which remains acceptable.
According to the invention, a driving assistance device for a motor vehicle includes at least one emitter of radiation toward the front of the vehicle, a receiver of part of this radiation reflected by a target vehicle, and control and calculation means for influencing the acceleration and braking of the following vehicle in accordance with the information coming from the emitter-receiver unit and in accordance with data pertaining to the following vehicle, and is characterised in that at least the emitter is mounted so as to be rotatable in terms of the azimuth and in that means for driving the emitter in rotation are provided in order to modify the azimuth of the beam of the emitter in accordance with the curvature of the road.
The receiver is preferably mounted so as to be rotatable with the emitter.
When the vehicle is fitted with a lighting optimisation system including means capable of providing information on the curvature of the road, control of the rotation of the emitter of the driving assistance device is advantageously performed on the basis of road curvature information gathered by the control unit of the lighting optimisation system.
The driving assistance device can be integrated into a headlamp.
The invention then allows the ACC driving assistance device to benefit from the functions of the lighting optimisation system. The driving assistance device no longer needs a costly angular motor drive and/or additional data interpretation.
The integration of the ACC driving assistance device into a headlamp allows it to benefit from features that protect it against rain and dirt and from any attitude correction, which allows simplification of the vertical scanning of the targets.
When the headlamp includes a rotary headlamp mounted on a plate that can rotate in terms of the azimuth about an essentially vertical pivot to ensure optimisation of lighting, the driving assistance device preferably includes an emitter mounted on the same rotary plate as the headlamp.
The rotary headlamp can be an additional headlamp, in particular fitted in the protective moulding of the vehicle, and at least the emitter of the assistance device is mounted on the rotary plate of the additional headlamp.
As a variant, the emitter can be mounted on a different, auxiliary plate rotatable in terms of the azimuth about a vertical pivot, rotational control of this plate being provided by the control unit of the plate of the headlamp. The auxiliary plate can be arranged in the same housing as the plate of the headlamp; a mechanism for transmitting the rotation of the plate of the headlamp to the auxiliary plate can be provided.
According to another possibility, the auxiliary plate is arranged in a different housing than that accommodating the plate of the headlamp.
A device for driving the auxiliary plate in rotation is controlled by the control unit of the plate of the headlamp.
The headlamp can include an additional fixed, pre-turned headlamp, the luminous intensity of which is controlled in accordance with the curvature of the road; the emitter is then mounted on an auxiliary plate rotatable in terms of the azimuth about a vertical pivot, the device for driving this plate in rotation being controlled by the control unit for the luminous intensity of the additional headlamp.
The receiver is preferably mounted on the same rotary plate as the emitter.
As a variant, the receiver is mounted in a fixed manner in a housing situated at the front of the vehicle, preferably in the central region. An emitter is mounted in both the right-hand and the left-hand headlamp, on the corresponding rotary plate.
When the vehicle is fitted with a lighting optimisation system controlling rotation in the horizontal plane of the headlamps, both toward the inside and toward the outside of a bend, a single emitter can be provided for the assistance device, this emitter being mounted either on the plate of the right-hand headlamp or of the left-hand headlamp.
In the case of a lighting optimisation system in which each of the headlamps can turn toward the outside to provide a BL function, each of the headlamps is fitted with an assistance device and the unit is set up so that the active side (side of the headlamp which is in the process of turning) inhibits the assistance device on the other side to ensure that only one assistance device is used at any one time.
Apart from the arrangements explained above, the invention consists in a certain number of other arrangements, which will be discussed more explicitly below in the context of embodiment examples described with reference to the attached drawings, which are in no way restrictive however. In these drawings: